Shock experiments in range of 10-45 GPa with small multidomain magnetite in porous targets

Peer reviewe

Compressed sensing FTIR nano-spectroscopy and nano-imaging.

Infrared scattering scanning near-field optical microscopy (IR s-SNOM) provides for spectroscopic imaging with nanometer spatial resolution, yet full spatio-spectral imaging is constrained by long measurement times. Here, we demonstrate the application of compressed sensing algorithms to achieve hyperspectral FTIR-based nano-imaging at an order of magnitude faster imaging speed to achieve the same spectral content compared to conventional approaches. At the example of the spectroscopy of a single vibrational resonance, we discuss the relationship of prior knowledge of sparseness of the employed Fourier base functions and sub-sampling. Compressed sensing nano-FTIR spectroscopy promises both rapid and sensitive chemical nano-imaging which is highly relevant in academic and industrial settings for fundamental and applied nano- and bio-materials research

The crystalline-to-amorphous transition in shock-loaded mullite Al2VI(Al2+2x Si2-2x)IVO10-x in the light of shear modulus anisotropy

We present experimental evidence for shock-wave induced amorphization in polycrystalline and single crystal mullite, Al2VI(Al2+2x Si2-2x)IVO10-x, at peak pressures above 35 GPa . The transition proceeds along a network of very thin glass lamellae (“planar deformation features” (PDFs)) of mullite-normative composition extending parallel to low-index crystallographic planes including {120}, {230} and {110}. Cumulative microstructural evidence from the PDFs derived via analytical transmission electron microscopy suggests a shear-induced for-mation mechanism. Experimental PDFs match the relative minima of the calculated represen-tation surfaces of the shear modulus suggesting that suitable PDF orientations can be derived from the elastic anisotropy of mullite. PDFs in mullite are in good agreement with those re-ported for naturally shocked sillimanite. Unlike the formation of shear-induced PDF-type glass lamellae in shocked mullite, the ther-mal decomposition of mullite following high post-shock temperatures results in a fine-grained phase assemblage consisting of corundum plus amorphous silica, and represents the most abundant transformation mechanism in the shock regime investigated (20-40 GPa). No stishovite was observed. At shock levels beyond 35 GPa thermal decomposition of mullite may occur along with PDFs within the same specimen

Characterization of semiconductor materials using synchrotron radiation-based near-field infrared microscopy and nano-FTIR spectroscopy

We describe the application of scattering-type near-field optical microscopy to characterize various semiconducting materials using the electron storage ring Metrology Light Source (MLS) as a broadband synchrotron radiation source. For verifying high-resolution imaging and nano-FTIR spectroscopy we performed scans across nanoscale Si-based surface structures. The obtained results demonstrate that a spatial resolution below 40 nm can be achieved, despite the use of a radiation source with an extremely broad emission spectrum. This approach allows not only for the collection of optical information but also enables the acquisition of near-field spectral data in the mid-infrared range. The high sensitivity for spectroscopic material discrimination using synchrotron radiation is presented by recording near-field spectra from thin films composed of different materials used in semiconductor technology, such as SiO2, SiC, SixNy, and TiO2

The phenomenology of attentional control: a first-person approach to contemplative science and the issue of free will

There are two basic aspects of attentional control. The ability to direct attention toward different objects is typically experienced as a fundamental indicator of attentional freedom. One can control what one attends to and directing attention is a relatively simple task. In contrast, sustaining attention on a chosen object proves to be difficult as mind-wandering seems to be inevitable. Does the problem of sustaining attention, mean that we are fundamentally unfree? We discuss this issue in light of an introspective study of directing and sustaining attention, looking specifically into the question of whether it is possible to experience the source of attention, i.e., the subject enacting freedom through attention. The study involved six persons performing different attention tasks over the course of about a month. Common experiences and contrasting reports are presented. This forms the basis for a discussion of the method of introspection and in particular of how to approach conflicting reports

Role of DNA Protection and Repair in Resistance of Bacillus subtilis Spores to Ultrahigh Shock Pressures Simulating Hypervelocity Impacts▿

Impact-induced ejections of rocks from planetary surfaces are frequent events in the early history of the terrestrial planets and have been considered as a possible first step in the potential interplanetary transfer of microorganisms. Spores of Bacillus subtilis were used as a model system to study the effects of a simulated impact-caused ejection on rock-colonizing microorganisms using a high-explosive plane wave setup. Embedded in different types of rock material, spores were subjected to extremely high shock pressures (5 to 50 GPa) lasting for fractions of microseconds to seconds. Nearly exponential pressure response curves were obtained for spore survival and linear dependency for the induction of sporulation-defective mutants. Spores of strains defective in major small, acid-soluble spore proteins (SASP) (α/β-type SASP) that largely protect the spore DNA and spores of strains deficient in nonhomologous-end-joining DNA repair were significantly more sensitive to the applied shock pressure than were wild-type spores. These results indicate that DNA may be the sensitive target of spores exposed to ultrahigh shock pressures. To assess the nature of the critical physical parameter responsible for spore inactivation by ultrahigh shock pressures, the resulting peak temperature was varied by lowering the preshock temperature, changing the rock composition and porosity, or increasing the water content of the samples. Increased peak temperatures led to increased spore inactivation and reduced mutation rates. The data suggested that besides the potential mechanical stress exerted by the shock pressure, the accompanying high peak temperatures were a critical stress parameter that spores had to cope with

Microbial rock inhabitants survive hypervelocity impacts on Mars-like host planets: first phase of lithopanspermia experimentally tested

The scenario of lithopanspermia describes the viable transport of microorganisms via meteorites. To test the first step of lithopanspermia, i.e., the impact ejection from a planet, systematic shock recovery experiments within a pressure range observed in martian meteorites (5–50 GPa) were performed with dry layers of microorganisms (spores of Bacillus subtilis, cells of the endolithic cyanobacterium Chroococcidiopsis, and thalli and ascocarps of the lichen Xanthoria elegans) sandwiched between gabbro discs (martian analogue rock). Actual shock pressures were determined by refractive index measurements and Raman spectroscopy, and shock temperature profiles were calculated. Pressure-effect curves were constructed for survival of B. subtilis spores and Chroococcidiopsis cells from the number of colony-forming units, and for vitality of the photobiont and mycobiont of Xanthoria elegans from confocal laser scanning microscopy after live/dead staining (FUN-I). A vital launch window for the transport of rock-colonizing microorganisms from a Mars-like planet was inferred, which encompasses shock pressures in the range of 5 to about 40 GPa for the bacterial endospores and the lichens, and a more limited shock pressure range for the cyanobacterium (from 5–10 GPa). The results support concepts of viable impact ejections from Mars-like planets and the possibility of reseeding early Earth after asteroid cataclysms

Predicting unplanned hospital readmission in palliative outpatients (PRePP) – study protocol of a longitudinal, prospective study to identify informal caregiver‑related and structural predictors

Background: Although the majority of German patients in a palliative state prefer to die at home, the actual place of death is most often a hospital. Unplanned hospital readmissions (UHA) not only contradict most patients’ preferences but also increase the probability of an aggressive end-of-life treatment. As limited knowledge is available which factors contribute to an UHA, the PRePP-project aims to explore predictors related to informal caregivers (IC) as well as medical and structural factors. - Methods: This prospective, observational, mono-centric study will assess structural and medical factors as well as ICs’ psychological burden throughout seven study visits. Starting in April 2021 it will consecutively include 240 patients and their respective IC if available. Standardized measures concerning ICs’ Quality of Life (WHOQOL-BREF), psychological distress (NCCN-Distress Thermometer), anxiety (GAD-7) and depressiveness (PHQ-9) will be assessed. If participants prefer, assessment via phone, browser-based or paper-based will be conducted. Medical records will provide routinely assessed information concerning patient-related characteristics such as gender, age, duration of hospital stay and medical condition. Nurse-reported data will give information on whether hospitalization and death occurred unexpectedly. Data will be progressed pseudonymized. Multivariable regression models will help to identify predictors of the primary endpoint “unplanned hospital admissions”. - Discussion: The PRePP-project is an important prerequisite for a clinical risk assessment of UHAs. Nevertheless, it faces several methodological challenges: as it is a single center study, representativity of results is limited while social desirability might be increased as the study is partly conducted by the treatment team. Furthermore, we anticipated an underrepresentation of highly burdened participants as they might refrain from participation

Shock experiments in support of the Lithopanspermia theory: The influence of host rock composition, temperature, and shock pressure on the survival rate of endolithic and epilithic microorganisms

Shock recovery experiments were performed with an explosive set-up in which three types of microorganisms embedded in various types of host rocks were exposed to strong shock waves with pressure pulse lengths of lower than 0.5 μs: spores of the bacterium Bacillus subtilis, Xanthoria elegans lichens, and cells of the cyanobacterium Chroococcidiopsis sp. 029. In these experiments, three fundamental parameters were systematically varied (1) shock pressures ranging from 5 to 50 GPa, (2) preshock ambient temperature of 293, 233 and 193 K, and (3) the type of host rock, including nonporous igneous rocks (gabbro and dunite as analogs for the Martian shergottites and chassignites, respectively), porous sandstone, rock salt (halite), and a clay-rich mineral mixture as porous analogs for dry and water-saturated Martian regolith. The results show that the three parameters have a strong influence on the survival rates of the microorganisms. The most favorable conditions for the impact ejection from Mars for microorganisms would be (1) low porosity host rocks, (2) pressures <10–20 GPa, and (3) low ambient temperature of target rocks during impact. All tested microorganisms were capable of surviving to a certain extent impact ejection in different geological materials under distinct conditions